Power transmission



Dec. 1, 1942.

R. S. MILLER POWER TRANSMISSION Filed Dec; 10, 1958 INVENTOR RAYMOND S. MILLER BY r- ATTORNEY Patented Dec. 1, 1942.

Raymond S. Miller, Detroit,

Mich., assignor to Victor: Incorporated, Detroit, Mich., a corporation of Michigan Application December 10, 1938, Serial No. 244,909

7 Claims. This invention relates to power transmissions,

- particularly to those of the type comprising two or more fluid pressure energy translating devices one of which may function as a pump and another as a fluid motor.

This invention is more particularly concerned with providing means for imparting a reciproeating movement to a slide or table such as is used, for instance, on grinders.

The usual reciprocating grinder has a table or slide on which the work element or the tool element is carried for continuous reciprocating movement during the grinding operation. During the actual working operation, this recipro cation is carried on continuously with automatic reversal at each end of the stroke-until the work is ground to the required size. When the work operation is completed it is necessary to retract the slide to separate the work and the grinding wheel for removal of the finished piece and replacement of a new work piece. For this purpose the slide is usually permitted to reciprocate beyond its normal limit of travel in one direction andis brought to a stop at the extreme limit of movement of the slide.

There have been numerous hydraulic transmission systems designed for operating a grinder of this class, many of them being rather cumbersome and requiring a large amount of piping and intricate control valves. Another defectcommon to systems previously proposed has been the inability to control the acceleration and deceleration of the slide at the ends of its normal working stroke with sufficient accuracy under all possible settings for speed and for length of stroke.

It is an object of the present invention accordingly to provide an improved power transmission system particularly adapted for operating grinders wherein the control valves may all be incorporated in a unitary panel which may be applied to a grinder with a minimum of piping connections and which provides improved operation of the grinder particularly with regard to maintaining any desired rate of deceleration and acceleration at each reversal of the slide.

It is also an object to provide a power transmission system of this character wherein the deceleration and acceleration are not subject to,

variation when thelength of stroke of the slide is adjusted or when the speed of travel of the slide is adjusted.

It is also an object to provide a transmission system of this character wherein the rate of travel of the slide may be maintained constant regardless of variations in the resisting load which the slide imposes on the power transmission system, yet which permits of ready adjustment of the speed of travel of the slide.

Another object is to provide a compact control panel to house the necessary valves for controlling the complete operation of the slide.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

Figure 1 represents a diagrammatic view of a grinder slide and control panel incorporating a preferred form of the present invention.

Figure 2 is a fragmentary view showing the construction of one of the dog-operated levers of the control panel.

Referring to Figure l, a pump l0 adapted to be driven by a prime mover such as an electric motor l2 has a suction conduit 14 through which fluid may be withdrawn from a tank I6 and delivered to a delivery conduit l8. The conduit l8 extends to a chamber28 of a relief valve 22 whioh'is in a control panel 24 and is adapted to bypass fluid to tank by a conduit 25 whenever a predetermined pressure is exceeded in the chamber 20. Chamber 28 is connected by a conduit 30 to a pilot relief valve 32. A conduit 34, which has a throttle valve 36 therein, extends from the chamber 28 of valve 22 to the pressure port of a pilot-operated five-way valve 38. The chamber 28 is also in communication with the conduit 34, beyond the throttle 36, through' a restrictor 26 communicating with conduit 30.

Valve 38 has a spool 48 which has lands 42,

44 and 46 that control cylinder ports 48 and 68 and tank ports 52 and 54. Lands 42 and 46 have slots 56 and 58 which connect by bores 60 and 62 respectively to the left and right end chambers of the valve 38. Land 42 also controls two pilot ports 64 and 66 and land 46 controls similar ports 68 and-l0. Conduits 12 and 14 extend respectively from ports 64 and 68 to similar adjustable needle valves 16 and I8. Conduits 88 and 82, having restrictions 8| and 83 therein, extend from needle valves I6 and 18 to ports 66 and 10 respectively. Similar check valves 84 and 86 are interposed between conduit and the left end chamber of valve 38 and conduit 82 and the right end chamber of valve 38.

Thecylinder ports 48 and 50 of valve 38 connect by conduits 88 and 98 to the left and right ends respectively of a cylinder 92. Reciprocably in cylinder l2 is a piston ll which carrod rod ll is secured to and de ll. Adiustably mounted of dogs Ill and "2; Rigidis a cam ill. The two of valve ll connect by conand Ill ports IIl'and Ill of a con III. Valve I has a spool Ill which controllingits various spool Ill has E 3H5 N] :5 tr? l valve lands-Ill and Ill for ill on slide ll is adapted to engage arm I2l at the end of its stroke when traveling to the left to shift valve spool ill to the right through shaft Ill and rod Ill. Dog Ill is adapted to engage a pin Il2 of a plunger Ill (see Figure 2) mounted in arm Ill at the end of its stroke when traveling to the right to shift valve spool Ill to the left. -A spring Ill holds the pin I32 in the path of dog Ill.

A chamber Ill around the section I22 of valve spool IIl connects by a conduit Ill to the tank conduit 2l. The valve III has pilot ports I42, I, Ill and Ill to control the shifting of valve llandalsohasendchambers Ill and Ill. A conduit Ill extends from the chamber 2l of relief valve 22 to the ports I and Ill. The ports I42 and Ill connect by conduits Ill and Ill and determinedbythesettingof pressure -Ingthroughbore2landconduitllwould thevalvelltomoveoifitsseattoopenchamber' l2. In such a case.

lltotankthroughconduiti'll.

With relief valve 22 seated. and with the valve valve ll. As the spool ll of valve ll is in (or promptly moves to) its left-hand position fluid is delivered to cylinder port ll and by conduit a to the right end or cylinder :2. The dotted Ill, port I and chamber Ill of valve Ill, conconduits ll and I! to check valves ll and ll vely. A conduit Ill, having restriction 2l therein,

extends from the portion of conduit ll between thethrottle valve ll and the flve-way valve ll to a starting valve Ill whose spool is spring biased to the right and which is manually operable by a pllmger ill. A controlled port N2 of valve Ill connects by a conduit Ill to the upper pbrt of a cam-operated valve Ill, which is normally spring biased upwardly and is held depressed by cam Ill acting on a roller ill of valve ill when the slide ll is at rest in its right-hand position. The lower port of valve Ill has a conduit Ill extending therefrom that connects to the two end chambers Ill and Ill of valve Ill. A drain conduit IIl connects valves l2, ll, Il2 and Ill to carryofl seepage therefrom. Conduit I'll also connects to conduit Ill. A conduit I12 connects between conduit I ll at the right of the restriction therein and the conduit ll leading to the control chamber 2l of re- .the pump Il, fluid is drawn from tank ll through conduit I4 and delivered by the pump Il through conduit Il to the chamber 2l of relief valve 22. The chamber ll of relief valve 22 is open to tank by conduits 3., I'll, III, valve Ill, conduit I,

valve Ill, conduit ill, and conduit Ill. Since the bore 2l is more restricted than this path, pressure fluid in chamber II will then cause valve 22 to move down to bypass the pump delivery to tank through conduit 2!. The solid line arrows show the directions of fluid flow during this operation. Under these conditions the machine will remain at rest.

To start a working cycle the plunger Ill is pushed to the left causing valve Ill to block port ill from conduit Ill. Pressure fluid passing through restrictor 2l to chamber 28 aided by spring pressure'now causes valve 22 to seat. For the present it may be considered as remaining seated duringoperation of the slide unless duit Ill and conduit 2l. As the cam Ill rides off of the roller ill of valve ill it will allow the latter to rise and block conduit Ill from conduit Ill. Plunger Ill may now be released to allow valve Ill to open conduit Ill to port I". This has no effect however on relief valve 22.as chamber 2l is now blocked from tank by valve Ill.

As theslide ll approaches the endofitsstroke to the left, adjustable dog "2 will rotate arm l2l and shaft I2l causing rod I24 to shift spool ill of valve ill to the right. Land Ill of spool IIl gradually will block port Ill to cut off the flow of exhaust fluid; from cylinder l2. This will have a throttling effect to gradually decelerate slide ll. Due to inertia of the slide, compression of oil on the exhaust side of the cylinder, elastic yield of the cylinder and pipes, and leakage across the spool from port I ll to chamber Ill, the valve spool III is carried completely across center.

-whenthespoollilhasbeenshiftedallofthe haust fluid from the right end of valve. ll passes at first from port ll, conduit 14, needle valve ll,

conduits l2 and Ill, port Ill of valve Ill, end

chamber Ill, conduit Ill to tank conduit Ill.

The slide ll will dwell at the end of its stroke until the land ll of valve ll opens port ll to the pressure port. The setting of needle valve ll determines the time required for valve spool ll to shift to the right which in turn determines the length of time of the slide dwell. when land ll first opens the port ll to pressure, slide ll will start back to the right at'a slow rate of speed but will accelerate as spool ll continues to move to the right. As the spool ll crosses center, land ll of spool ll blocks por't' ll but exhaust fluid then passes through bore l2. slot ll, port 'Il, conduit l2 and restriction ll and conduit Ill to tank as previously described. The restriction ll retards the flow of exhaust fluid from the right end of valve ll to impart a smooth acceleration to the slide, much the same as the needle valve II but at a diflerent rate.

When port ll was connected to the pressure port of valve ll, fluid was delivered through conduit ll to the left end of cylinder l2 to cause piston ll to move to the right and carry slide the ":5 n therewith. Exhaust fluid from the right of The piston ll ac v piston 94 returned to tank through conduit 80, ports 80 and 84 of valve 38, conduit I08, port H2 and chamber I38 of valve H4 and conduit I40 to the tank conduit 25. The directions of flow during rightward shifting of valve,40 and rightward travel of piston 94 will be opposite to that shown by the dotted arrows as the circuit is symmetrical.

The slide 88 will continue to move to the right I until adjustable dog Il.contacts pin I82 of arm I38 (Figure 2) to revolve the latter to the right. This will shift valve spool II8 of valve II4 to the left. Land I20 of valve spool II8 gradually closes port II2 from chamber I38 to decrease the flow of exhaust fluid from cylinder 92 to thereby decelerate the slide 98 and when the flow is stopped to cause the slide to dwell.

When spool II8 has been shifted completely to the left port I46 is opened to port I48 to direct pilot pressure from chamber 20 of relief valve 22 through conduit I54 and check valve 88 to the right end of valve 38 to shift its spool 40 to the left. The resulting actions are similar to those described when the spool was shifted'to the right. Exhaust fluid passes at first from port 84, through conduit I2, needle valve 18, conduits 80 and I52, port I42 and end chamber I41 of valve II4, conduit I88, and conduit I10.

The slide 98 will dwell at the end of its stroke until land 44 of valve spool 40 opens port 50 to the pressure port. The setting of needle valve to Harry F. Vickers,

matically operates the relief valve to maintain a variable pressure in the chamber 20, which pressure corresponds exactly at any .instant to the pressure in the cylinder 92 plus an increment determined by the spring bias on the piston 22. This phase of operation of the piston 22 and throttle 38 is described more fully in the patent To bring the slide to a rest the plunger I34 in arm I30 is pulled out against the bias of spring I38 to remove the pin I32 from the path of dog I00. On the next stroke of the slide to the right the dog I00'wl1l not contact pin I32 to shift valve spool II8; therefore piston 94 will continue to carry slide 98 to the ght until cam I04 contacts roller I81 to depress valve I88. The relief valve 18 determines the time required for valve spool 40 to shift to the left, the period of dwell of the slide and the acceleration of the same in the opposite direction. The opening of land 44 will accelerate the slide in its movement to the left. The path followed by the fluid is the same as on the first stroke. When land 42 blocks port 84 exhaust fluid from the left end of valve 38 will pass through bore 80, groove 58, and port 88 until valve 38 reaches the limit of its travel. From port 88 the flow will be through conduit 80, restriction 8|, conduit I52, port I42 and end chamber I41, conduit I88 and conduit I10 to tank.

The slide 98 will continue to reciprocate as described, namely with automatic predetermined deceleration at the end of each stroke, predetermined period of dwell and a predetermined rate of acceleration.

The relief valve has a further function in conjunction with the throttle 33 of controlling the rate of travel of the slide 98 during the constant velocity portion of the cycle. that the piston 22 is subject on the pressure in conduit 34 It will be noted its upper side to ahead of the throttle 38 and is subject on its lower side to the pressure in the conduit 30 beyond the throttle 38. Thus the net hydraulic force exerted on the piston 22 depends on the pressure drop through the throttle 38. Should this pressure drop tend to increase, the piston 22 will be forced downwardly, thus opening the valve slightly to permit a portion of the oil delivered by the pump III to bypass to tank through conduit 25.

It will be seen that under all conditions an equilibrium position of the valve 22 is reached wherein suflicient oil is by-passed to maintain a fixed pressure drop through the throttle 38. With a fixed pressure drop through the throttle 38 it follows that the rate of flow therethrough is correspondingly fixed. Thus the velocity of the slide is maintained constant independently of variations in resisting load applied to the slide 98. In other words,

the piston 2: auto- 22 is thereby vented and the pump passed as previously described and comes to rest. 'Another cycle of operation may be started by pushing in plunger I80.

While the form of embodiment of the invention, as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid conduits forming supply and return connections between the pump and motor, a pilot valve shiftable in opposite directions by the motor, a valve in said connections for controlling the fluid flow to the motor and controlled by the pilot valve, means including a three-way valve in series with the control valve and operated by the motor after predetermined movement thereof for blocking the return connection from the motor, means associated with said two last-mentioned valves for re'establishing flow in said return connection after the control valve has been shifted, a relief valve in the supply connection, a manually adjustable throttle in the supply connection, and means for controlling said relief valve to maintain a predetermined pressure drop through said throttle.

2. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid conduits forming supply and return connections between the pump and motor, a pilot valve shiftable in opposite directions by the motor, a valve in said connections for controlling'the fluid flow to the motor and controlled by the pilot valve, means including a three-way valve in series with the control valve and operated by the motor after predetermined movement thereof for blocking the return connection from the motor, means associated with said two last-mentioned valves for reestablishing flow in said return connection after the control valve has been shifted, a relief valve in the supply connection, a manually ad justable throttle in the supply connection, means including a piston exposed to pressure ahead of and beyond said throttle for controlling said relief valve to maintain a predetermined pressure delivery bythe slide 98 drop through said throttle, and means for unmovement ofthe control valve, and means fonning a by-pass around said restriction for causing controlled motion of said control valve, said bypass beins opened by movement of the control.

valve to a predetermined positiona'nd having predetermined resistance for controllins the rate of movement of the control valve and the acceleration of fluid motor, said control valve having a range of movement before opening said bypass during which'the control valve ineflective to oheflle connections between the pump and flrst motor.

4. In a hydraulic power transmission system the combination of a pump. a fluid motor, a pilot valve shiitable in opposite directions by the motor, a valve for reversing the direction of fluid flow to the motor, reversible auxiliary fluid motor means for operating said reverse valve in opposite directions and controlled by the pilot valve, a pair of independently adjustable restrictions for controlling the speed of movement of the reverse valve, and means forming a by-pass around each restriction for causing controlled movement of the reverse valve, said by-passes being opened and closed by movement of the reverse valve and having predetermined resistance for controllin the rate of movement of the control valve and the acceleration of the fluid motor, said reverse valve ha a range of movement before opening a by-pass during which the control valve is ineffective to change connections between the pump and flrst motor.

5. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid conduits form'- ing supply and return connections between the pump and motor, a five-way reverse valve in said connections for controlling the fluid flow to and from the motor, said reverse valve including duplicate return connections, one for each side of the motor, and a three-way valve operated by the motor at opposite limits of its travel and connected with said duplicate: connections to selectively block whichever of them is at the moment carrying the return flow from the motor while unblocking the other whereby the motor when the three-way valve-is shifted and isrestartedinthe oppositedirectiononlyafter the reverse valve is shifted.

7. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid conduits formin supply and return connections between thev.

pump and motor, a pilot valve shiftable in opposite directions by the motor, a flve-way reverse valve in said connections and controlled by the pilot valve for controlling the fluid flow to and from the motor, said reverse valve including supply and return connections, one of which is duplicate, one for each side of the motor, and a three-way valve operated by the motor at opposite limits of its travel and connected with said duplicate connections to selectively block whichever of them is at the moment carrying the return flow from the motor while simultaneously unblocking the other whereby the motor is stopped when the three-way valve is shifted and is restarted in the opposite direction only after the reverse valve is shifted, said pilot valve and three-way valve being connected together for simultaneous operation.

. RAYMOND S. MILLER. 

